1. Technical Field of the Invention
The present invention relates to the production of magnetic films with protective layers, and more specifically to the deposition of a protective film on top of a magnetic film which is used as a data recording layer on a data recording disk.
2. Description of Related Art
Data recording disks such as hard disks and CD-ROMs are already well known. Data recording disks of this sort are constructed by forming a recording layer on which data is recorded on the surface of a substrate made of metal or a dielectric material. The recording layer is produced by subjecting the substrate to surface processing. This surface processing is described below, taking the production of a hard disk as an example.
In the production of a conventional hard disk, a metal foundation film of Cr, or the like, is produced by sputtering onto a substrate made of aluminum coated with NIP, and then a magnetic film of CoCrTa, or the like, is formed as a recording layer by sputtering thereupon. A protective film consisting of a thin carbon film, or the like, is then provided on top of the magnetic film by a similar sputtering process as used to deposit the foundation film or magnetic film, thereby producing the finished hard disk.
In the above-mentioned data recording disk, the protective film on top of the magnetic film is provided to protect the magnetic film against collisions and wear from the record/playback head and to ensure its durability, and must be a solid film with lubricating properties. On the other hand, to increase the recording density, the protective film should be made thinner. That is, as the recording density increases, the distance between sectors decreases. As the distance between sectors decreases, the distance between the magnetic film and the record/playback head also has to be made smaller. In other words, the protective film has to be a small thickness while maintaining sufficient hardness.
To meet such demands, studies have been made into the deposition of protective films by chemical vapor deposition (CVD) instead of conventional sputtering. CVD is a procedure in which a prescribed precursor gas is activated by conferring energy to it, and a gas-phase reaction is used to deposit a prescribed thin film on a substrate. When CVD is used to deposit a thin carbon film as a protective film, a hydrocarbon gas such as CH4 is used. A plasma is then produced by conferring energy to this CH4 or other gas. The CH4 or other gas dissociates in the plasma, and a carbon film is deposited as the carbon produced as a result of this dissociation reaches the surface of the substrate.
In a CVD process using a hydrocarbon gas of this sort, it is possible to deposit a so-called diamond-like carbon (DLC) film. A DLC film is a film formed by carbon that dissociates from the precursor gas and crystallizes with a diamond-like structure on the surface of the substrate. Since a DLC film has a diamond structure, it is expected that it can be made thinner and harder than a film deposited by sputtering using a graphite target.
However, no reports have been made regarding the optimal deposition conditions for protective films of this sort. Therefore, on researching the optimal deposition conditions for protective films, it was found that there is a constant problem from the mutual differences between the optimal deposition conditions for the magnetic film deposited before the protective film and the optimal deposition conditions for the protective film.
The present invention has been made to solve such problems, and has the technical merit of solving a problem that arises due to differences between the optimal deposition conditions for the magnetic film deposited before the protective film and the optimal deposition conditions for the protective film.
The present invention relates to a method for depositing a protective film on top of a magnetic film on a substrate, and wherein the protective film deposition temperature, which is the temperature of the substrate when the protective film is deposited, is higher than the magnetic film deposition temperature, which is the temperature of the substrate when the magnetic film is deposited, and the substrate is heated to the protective film deposition temperature when the protective film is deposited after the magnetic film has been deposited.
The present invention also relates to an apparatus for depositing a thin film on top of a magnetic film on a substrate, and the protective film deposition temperature, which is the temperature of the substrate when the protective film is deposited, is higher than the magnetic film deposition temperature, which is the temperature of the substrate when the magnetic film is deposited, and is equipped with a heating mechanism whereby the substrate is heated to the protective film deposition temperature when the protective film is deposited after the magnetic film has been deposited.
The above-mentioned apparatus may also be provided with an intermediate heating chamber which is equipped with the heating mechanism. This intermediate heating chamber may be provided between a magnetic film deposition chamber in which a magnetic film is deposited on the surface of the substrate, and a protective film deposition chamber in which a protective film is deposited and laminated on top of this magnetic film, and airtight connections may be made between the magnetic film deposition chamber and intermediate heating chamber and between the intermediate heating chamber and the protective film deposition chamber, whereby the magnetic film deposition, intermediate heating and protective film deposition can be performed successively without exposing the substrate to the atmosphere.
Alternatively, the protective film deposition chamber of the above-mentioned apparatus may deposit a protective film by plasma chemical vapor deposition and may be equipped with a biasing mechanism that applies a high frequency voltage to the substrate whereby a negative bias voltage is conferred to the substrate through the interaction between the high frequency and the plasma, causing positive ions in the plasma to impinge on the substrate.
Or, the protective film deposition chamber of the above-mentioned apparatus may be equipped with an ion source and may deposit a protective film by ion beam vapor deposition.
In addition, the protective film deposition chamber of the above-mentioned apparatus may be equipped with a plasma forming means that forms an electron cyclotron resonant plasma, and plasma chemical vapor deposition may be performed by the plasma formed by this plasma forming means.